Digital audio content is downloaded and played on a computer using an application such as an MP3 player. MP3 is short for MPEG Layer 3 (Moving Pictures Expert Group) and refers to a format for storing digital audio.
A Secure Digital Music Initiative (SDMI) has been formed to prevent unauthorized copying and playing of digital audio content. SDMI compliant systems include any device, software application, or any other system that conforms to the requirements of the SDMI specification. Version 1.0 of the SDMI Portable Device Specification, Part 1, document No. pdwg99070802, was published on Jul. 8th, 1999.
Most SDMI compliant software and hardware devices being introduced onto the market today import content into an SDMI Local Environment before storing the content on a computer. The SDMI Local Environment refers to a subset of the environment where all SDMI rules and behaviors are obeyed. One SDMI rule is that unencrypted content must be watermark screened before the content is stored in the SDMI Local Environment. Importing content directly into the SDMI Local Environment is beneficial to a user because the time-consuming watermark screening process required by SDMI is only done once at storage rather than each time the content is downloaded or played out to a device.
Importing unencrypted content directly into the SDMI Local Environment requires that the content be encrypted as SDMI content to remain persistently on the user""s computer after watermark screening. Storing encrypted content introduces several usability problems for the user. Once the digital content is encrypted in the SDMI Local Environment, SDMI default usage rules restrict the user""s ability to copy the SDMI content to non-SDMI devices. However, a user may want to use the digital content on both SDMI compliant devices and non-SDMI compliant devices. Because of these SDMI restrictions, the user has to store one SDMI encrypted copy of the content for the SDMI compliant devices and store one unencrypted copy of the content for use with the non-SDMI compliant devices. Storing both encrypted and non-encrypted content files wastes computer disk space and prevents interoperability of any one content file with all content players.
Audio content may be played directly from a software application run on a Personal Computer (PC) or may be downloaded and played on a Portable Device (PD). Most SDMI compliant software and hardware devices use security protocols and encryption software that establishes a Secure Authenticated Channel (SAC) between the Personal Computer and the Portable Device. The content is first encrypted in a SDMI Local Environment that resides on the PC. The encrypted content is then transferred from the PC to the to the PD over the SAC. The software for establishing the SAC is complicated and tends to be expensive since the software must be tamper resistant.
The present invention addresses this and other problems associated with the prior art.